Should 25,0 Riyals be returned to the Zakat Fund after selling the car, especially since the car was sold one month after receiving the amount from the Zakat Fund?

If you took from the Zakat money to pay off your debt, or part of it, and spent it for that purpose, then you are not required to return it. This is because those in debt (al-gharimun) receive funds in a considered manner, and if the money is spent for the purpose for which they were entitled to receive it, it is not reclaimed from them.